1. Field of the Invention
This invention relates to an electrical junction box, and more particularly to an electrical junction box provided for wiring up an automobile.
2. Description of the Related Art
In wiring up an automobile, in order to simplify the wiring of the wire harnesses, an electrical junction box is used which is to collectively arrange relays and fuses. In the electrical junction box, circuits made up of bus bars formed by pressing copper or brass plates are provided in a plurality of layers.
In the electrical junction box, a wiring board which is an insulated substrate is provided, and a tab raised at one end of a bus bar arranged on the wiring board is inserted in a connector mounting section of a main cover, and another tab raised at the other end of the bus bar is passed through the wiring board and inserted in a connector mounting section of an under cover.
Recently, automobiles have been markedly improved in performance, and accordingly increased in the number of electrical components, and in the number of circuits to be held in an electrical junction box. Hence, depending on the model or grade of an automobile, it is often necessary to change the electrical circuit of the electrical junction box. In such a case, heretofore an electrical junction box is newly prepared which has bus bars specially designed for the circuit thus changed.
However, the above-described conventional electrical junction box suffers from the following difficulties: That is, in order to form the required electrical junction box, components for realizing the given circuit must be newly arranged, and particularly the bus bars specially designed therefor must be newly manufactured. Thus, the employment of the conventional electrical junction box is not practical in the saving of cost and time.
On the other hand, a technique is known in the art that a main electrical junction box having a fundamental circuit is connected to an auxiliary electrical junction box, to increase the electrical function thereof. However, the technique is disadvantageous in that the electrical junction boxes each has a relatively large unwanted space, and occupy a relatively large installation space.